DESCRIPTION (Applicant's Description): Malignant primary brain tumors, especially gliomas, are characterized by a propensity to invade surrounding brain structures resulting in a high rate of local recurrence and a dismal clinical outcome. The invasion process is a complex cascade of events. A l though multiple mechanisms may be involved, it appears that focal proteolytic activity is needed for extracellular matrix (ECM) remodeling and s u bsequent invasion. The plasminogen-plasmin system directly or, by activating matrix metalloproteinases (MMPs) has been implicated in the proteolytic remodeling of ECM. Annexin II (Ann II), a newly identified endothelial cell surface protein, is a co-receptor for plasminogen (PLG) and its activator, tissue plasminogen activator (t-PA). Ann II increases the catalytic efficiency of plasmin generation up to 60-fold over baseline in a purified protein system. We have employed C6 rat glioma cells, a well-defined in vitro model of human high grade glioma to study the potential role of Ann II in plasmin - mediated invasion. Preliminary in vitro data suggest that C6 cells abundantly express annexin II (Ann II), enhance plasmin generation in functional studies and mediate t-PA-dependent migration of C6 cells through both collagen and laminin matrices. Also, the invading edges of high grade human gliomas show strong positive staining for Ann II in the tumor cells. Based upon these preliminary data, this project will test the hypothesis that Ann II plays a role in plasmin - mediated high grade glioma invasion. The research will focus on defining the role of Ann II in vitro using invasion and matrix degradation assays, radiolabeled binding assays, specific functional assays and substrate zymography. Also, the hypothesis will be tested in an in vivo system with stereotactic injection of C6/lac Z cells into Fischer rat brains to produce tumors and to inhibit invasion with anti-Ann II antibodies and anti-sense Ann II constructs. Human brain tumor sections will be studied immunohistochemically for Ann II, t-PA expression and plasmin activity. By understanding mechanisms of invasion, it may be possible to devise novel therapeutic approaches to brain tumors specifically targeted to limit Ann II - mediated invasion. These studies could also have far reaching implications for the diagnosis and treatment of other locally invasive and metastatic tumors in a wide variety of settings. The principal investigator for this application is a board certified pediatrician, who during the process of training in pediatric hematology/oncology has spent 2 years in a vascular biology laboratory under the direction of Dr. Katherine A. Hajjar. The proposed plan will continue under her supervision at Weill Medical College of Cornell University. Her lab is part of a Specialized Center for Thrombosis Research and a Program Project in Vascular Biology, and is well equipped to carry out the investigations. Apart from weekly lab meetings to discuss individual projects, weekly research seminars and journal clubs provide an opportunity to meet with other investigators at the medical college and exposure to new ideas. Dr. Hajjar is also very accessible for individual weekly meetings when the need arises. T h i s environment will provide excellent training for a developing physician-researcher.